1 files changed, 26 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/IDeltaBag.java b/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/IDeltaBag.java
new file mode 100644
index 00000000..99a4cb3b
--- /dev/null
+++ b/subprojects/viatra-runtime-matchers/src/main/java/tools/refinery/viatra/runtime/matchers/util/IDeltaBag.java
@@ -0,0 +1,26 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2017, Gabor Bergmann, IncQueryLabs Ltd.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.matchers.util;
+
+/**
+ * An {@link IMemory} that represents the difference between two states of a set or {@link IMultiset}, and therefore
+ *  may contain values with a negative multiplicity.
+ * 
+ * @author Gabor Bergmann
+ * @since 1.7
+ */
+public interface IDeltaBag<T> extends IMemory<T> {
+    
+    @Override
+    default boolean removeOneOrNop(T value) {
+        // makes no difference for delta bags
+        return removeOne(value);
+    }
+
+}